Composite structure embodying shear connectors



Aug. 16, 1949. c. CUENI 2,479,476

COMPOSITE STRUCTURE EMBODYING SHEAR CONNECTORS Filed April 25, 1944 3Sheets-Sheet 1 6 J 1/ /z flfik,

. INVENTOR. C/i/Wf/Yf R Cur/w A fray/Y1? Aug. 16, 1949. I c. P. CUENI.2,479,476

COMPOSITE STRUCTURE EMBODYING SHEAR CONNECTORS Filed April 25, 1944 5Sheets-Sheet 2 INVENTOR.

ATTORNEX.

Aug. 16, 1949. c. P. CUENI 2,479,476

COMPOSITE STRUCTURE EMBODYING SHEAR CONNECTORS Filed April 25, 1944 r sSheets-Sfieet 5 INVENTOR. C/t'Mf/Vf A Caz/w ATTORNEY.

Patented Aug. 16, 194

comosrfrn STRUCTUREEMBODYING SHEAR CONNECTORS Clement If. Cuen'i,Rutherford, N. .11, assignor to Porete: Mfg; Company, North Arlington,N. J soorporatiom of New Jersey Application April"v 25, 1944, Serial.No. 532,608

The present invention is directed to composite structures consistingessentiallyof metal. beams and reinforced concrete slabs supported bythe same and united thereto byshear reinforcements.

It has been customary for a number of years to provide structures ofthis kind wherein the upper flangesof the steel beams, either rolled orfabricated, were" provided with shear connectors in the shapeof ahelix,usually called a spiral, or in the shape of a waved line, or of anyother serpentine or sinuous form; asset forth in Patent 2,016,616, datedOctober 8, 1!?35. These steelrods were welded tothe top flange of thesteel beams and well embedded inthe' concrete'; Such shear connectorshave proved to bevery emcient in actual constructions and in tests.However", in numerous tests it was brought out that all these barconnectors have one weak" spot, namely, at the points where the spiralis welded to the flange. 'I-h-is occurssometimes due to defectiveweldingwhich may result in burning away some of the metal orchanging the fiberof the metal, and thus create a: weakness at the points where maximumstrength is necessary:

The present invention is intended and adapted to provide a structure ofshear reinforcement which has all of the advantages of the continuoustype and which obviates the disadvantages thereof, it being among theobjects thereof to provide a composite structure having shear re}-inforcement which is continuous, easy to" apply, and has maximumstrength at the areas of max lmu-mstress, I

It is also among" the objects of the present in mention to provide ashear reinforcement which may' be out from standard pieces with" aminimum of waste, whichis economical to' produce, and which may be easilyand readily welded to the -bearr-i thefield.

In practicing the present invention, anumber of considerations must betaken into account. The minimum unit stress in the described barconnectors is approximately at their highest point between two welds,and the maximum unit stress near the welds. point on the-bars close tothe Welds is weakened by the welding; The welder by striking-the are tostart the weld may burn some of the bar ofli and the welding heat makesthe bar" steelmore brittle and thus; more liable to Break, especiallyunder repeated loadiliga the points near the welds are considerablyweaker than the rest of the bar, and if this condition can be changedthe shear corn nectar becomes more effective and more reliable.

actual tests have" demonstrated, that there is also a-weak spot for theconcrete near the welds, especially so on thccom ression side of eachweld of a continuous bar connector. When load is applied on a compositestructure the bond of the concrete to the too flange of the beam isfirst destroyed and then'the shear connector begins toact, because it istheir the only means that can prevent relative movement between thesteel beamand the concrete slab: This is achievedpartly by pressureexerted by the concrete on the bar.- If the pressure increases until theelastrcally embedded bar begins to bend, thercwillbe some relativemovement between concrete and steel beam and the local pressure ontheconcrete near the welds will increase considerably; Finally anexcessivebcdd irig pressure on the concrete near the welds results,followed by a crushing of the concrete, which in: turn will cause anincrease in the bending or the bar, which is more protected by strongconcrete; This re stilts im the: breaking' phenomena as follows:Formation. oft cracks in the: concrete with; ultra mate; breakage; orthe connector bEiTSl near the welds It is concluded, therefore, that amore rigid: bar near the welds, or a bar that presents a larger:compression area. to the concrete near the welds, or a"- bar that isreinforced near the welds does not onlyhelp the bar, but also the:concrete, andiwill increase the efliciency of aconnector considerably.-

Such a strengthening oil the connector bars near the welds can. beachieved by using, bars of. variable cross section bent in such a. waythat the heavier cross section is at the bottom where the, bars arewelded to the Steel beam.

It also can be achieved by strengthening the bar connector by usingwithiit a small rigid sheaf connector welded to the top flange of thesteel beam: as close to the welds of the bar' connectors as possible.

In the accompanying drawings constituting a part hereof, and in whichlike referencecharacters indicate like parts? Fig. 1 is a perspectiveview of a beam-with a serpentine shaped shearconnector of variable crosssection, togetherwith a portion of the con-"- crete slab whichreststhereon and is united thereto; Fig. 2' is a longitudinal crosssectionalView 01 the structureof Fig. 1, showing my a portion of' the concreteslab; V q

Fig; 3 showsaz sheet of metal from which the connectors shown in Fig-s.I and 2 ean'easil'y be- Theoretical investigation has indicated, and asoutwith a minimum of Waste or material;

heat.

Fig. 4 shows a transverse, cross-sectional view of a composite section,the concrete slab being shown in dotted lines;

Fig. 5 shows a longitudinal view of the section shown in Fig. 4;

Fig. 6 shows a plan view of the same section;

Fig. 7 a plan view of a similar section, using a different form ofcontinuous bar;

Fig. 8 shows a longitudinal cross-sectional view of a beam with shearreinforcement adjusted to the actual shear; and

Fig. 9 shows a plan view of the same section.

A composite section generally consists of a steel beam I, only partlyshown in Fig. 1, a top flange 2, a shear connector 3, and a concreteslab 4. Shear connector 3 is cut from a sheet of metal in such a waythat a bar or strip is formed where a greater width 5 alternates with asmaller width 6 and then the bar is bent and welded to the top flange 2in such a way that the wider part 5 contacts the top flange 2, and thesmaller part reaches up into the concrete slab 4. The welds l are at thewide part 5 of the bar, so that if the welding weakens the material thebar will have enough strength left to perform its purpose. At the sametime the greater width of the bar provides a larger compression area forthe concrete near the welds where it is most required. Such a barconnector eliminates the weak points of the heretofore used shearconnectors of spiral or serpentine shape, and, per unit weight, is muchmore efiicient and therefore more economical.

In order to make the welding 'l' easier, the shear reinforcement bar isbent in such a way that the wide part represents a straight flat area,fitting well the top flange 2 of beam I. tine shaped connector of theprior art consisting of a round or square bar is liable to split theconcrete, and, as explained before, has a weak spot for the steel andthe concrete near the welds. A connector as shown in Figs.. 1 and 2 doesnot have these disadvantages. At the contact areas with the top flangethis connector is so much widened that it will not matter much if thewelder burns part of it off. The bar is so wide at the place of the twowelds that not all of the material will become brittle by the welding Acompression surface of considerable width is presented to the concreteso there is no danger that the local pressure of the concrete near theWelds becomes critical. Due to the considerable width of the bar thereis less danger of splitting the concrete.

The connectors according to the present invention are therefore moreeflicient and require less material, as they can be out without muchwaste from sheet metal. How this can easily be done is shown in Fig. 3.From a steel plate 8, or piece of sheet metal, connectors 9, III, II andI2 can be cut off leaving only the waste shown by the small pieces I3.The cutting will require special shearing plates or cutters, but withone set, a series of shear connectors that can meet quite a number ofdifferent conditions, can be made. The thickness of the steel plate canbe increased for greater unit shear, or the width of the strips can beincreased as shown by I0, II and I2. Two connectors or more can bewelded parallel to each other and longitudinally on top of a beam.

If the depth d of the connector, as shown in Fig. 2 has to be increased,the length of the pitch 1 can be reduced. For instance the same lengthof bar is required for a connector with d=6 and.

A ser pen- 4 1:8 as is for a connector with d=4" and 1:12", or d=5" andZ=10.5

In principle a bar of variable cross section could also be used tomanufacture a shear connector of helical shape; however, the dimcultiesencountered in making the spiral in such a way that the heavier part ofthe bar is at the contact points with the top flange are much greaterthan bending a bar of variable cross-section into serpentine shape.

Another way to reinforce the continuous bar connectors, and achieve theimprovements described before is shown in Figs. 4, 5 and 6. Shearconnector I4 consisting of a rectangular bar of serpentine shape iswelded to the top flange 2 of the I-beam I. A round bar could be used aswell, though the rectangular bar presents a larger coil-- pression areato the concrete.

A small piece of angle I5 is placed under bar I4, tack welded theretoand also welded to the top flange 2, as close as possible to theconnector weld]. Such small angles can be welded on both sides of theconnector weld as shown by It and I1. They may be perpendicular to thetop flange 2, as shown by IE3 or inclined toward the center of the beamas shown by IT. Instead of angles small Z shapes I8 may also be used, orsmall T shapes I9. Because the depth of the stiffening connectors isvery small a triangular or rectangular plate 28 may be as eflicient asthe angles and the T and Z shapes, if the plate is well tack welded tothe connector bar I4.

All these stiffening connectors used as shown in Figs. 4 to 6 stiffenthe bar connector near its weakest point, prevent the concrete frombeing locally overstressed near the welds and also reduce the danger ofthe concrete being split by the bar connector. Because these stiffeningconnectors present a comparatively large compression area to theconcrete they help considerably in transmitting the horizontal shearinto the concrete slab. Therefore, they do not cause an additionalexpense. The bar connector is designed for the remaining shear only andthe saving in cost in the bar connector well offsets the cost of thestiffening connectors.

Fig. 7 shows that the stiffening connectors I6,

I8, I9 and 20' can easily be applied to a helix shaped shearreinforcement or connector 2| fastened by welds 7 to the top flange 2.Instead of equal legged angles I5 and I1, angles with unequal legs 22and 23 may be used.

It is very seldom that a composite section has a uniform unit horizontalshear throughout the full length. The unit horizontal shear is usuallyat its maximum at the supports and decreases toward the center of thespan. It is complicated to adjust the continuous bar connectors to theactual shear because these bar connectors cannot be madeeconomically-with a variable pitch. By using stiffening connectorstogether with the continuous bar connectors the shear reinforcement of acomposite beam can easily and economically be adjusted to the actualshear. An example of such a shear reinforcement is shown in Figs. 8 and9. 7

Beam I rests on support 25 of which 26 shows the center line. 21 is thecenter line of the span. Line 28 is the computed shear line. Thecontinuous shear bar connector 24 is designed for a unit shear of 29.This uniform shear line intersects the actual shear line at point 30,which means that from this point on to the left, the shear connector 24is insufficient for transmitting the horizontal shear. A heavier barconnector could be usedfrom hereon, or: the pitch. 1' of the connectorcould bereduced, As an alternative, is sma ljstiifenine: plate at iswelded to the flange Les. close as. possible to welds l of the barconnector 24. This; plate not only stiffens the bar nnector- .24, but"also transmits some shear through compression on the concrete. At point32 the combined capacity of transmitting shear of bar connector 24 andstiffening, connectors. 3| is used up. Therefore, the height, of; the,stiffening connectors 33 may be increased and also the width ofstiffening connector 34. If one stiffening connector is unable to. makeup the differencebetween the computed unit shear and the shear thatcanbe transmitted bythe bar conneetor, two stiffening connectors may beused per pitch of bar connector, one on, each side of weld has shownbyconnectors 35. One of the two may be; of smaller dimensions. For thenext bar pitches the compression areas of the stiffening connectors aregraduallyincreased to take care of the. increasing horizontal shear, asshown by conne t stt and 3.

Angles 38 may be used as well as plates. The connectors 31 and 38 areinclined toward the center of the span to help the bar connector 24 toprevent uplift of the concrete slab. As shown by dotted line 39 theactual shear reinforcement can closely be adjusted to the computed shearline 28, either every pitch or every second or third pitch of thecontinuous bar connector.

The illustrations shown shall in no way restrict the invention. Otherstiffening connectors may be used and the manner of application and thearrangement may vary. Other types of bar connectors with variable crosssection may be used to achieve the purpose of improving the heretoforeused continuous connectors. The beams may be rolled or fabricated andboth the beams and the connectors may be of a metal other than steel.The composite structures may include the usual reinforcing rods or meshcommonly used in concrete, in addition to the shear connectors. Althougha number of different forms of small connectors have been described,many other forms are suitable for the present purpose. By the termwelded or the like used in the claims, it is intended to include thevarious known methods, such as torch welding, electric welding, contactor pressure welding, and the like.

These and other variations in the details of the invention may be madewithin the spirit thereof, and the invention is to be broadly construedand to be limited only by the character of the claims appended hereto.

What I claim is:

1. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a plurality ofspaced intervals along the centerline of said flange and Welded theretoat the areas of said contacts, the portions of said reinforcementintermediate said areas extending upwardly a substantial distance abovesaid flange, said reinforcement comprising a flat bar, the under face ofsaid bar being flat on said flange and providing said contacts.

2. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a plurality ofspaced intervals along the centerline of said flange and welded theretoat the areas of said contacts, the portions of said reinforcementintermediate. said areas extending upwardly a. substantial distanceabove said flange, said reinforcement compri ing a flat bar,theunderface. of said bar being flatv on said flange and providing saidcontacts, said welds being at the lateral edges, only of said bar.

3. In. a composite. metal-concrete structure a metal beam having. anupper flange, a continuous sinuous metal shear reinforcement welded onsaid j flange, said reinforcement contacting said flange.

at'a. plurality of spaced intervals and welded thereto at. the. areas ofsaid contacts, the portions of said reinforcement intermediate saidareas extending upwardly a substantial distance above said flange, saidreinforcement comprising a flat bar, the under face of said bar beingflat on said flange. and providing said contacts, the width of sa' 'ibarbeing. greatest at said areas, and decreesintermediate said areas.

In a composite metal-concrete structure a metai beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflan e, said. reinforcement contacting said flange at. plurality ofspaced intervals and welded thereto at the areas of said contacts, theportions of said reinforcement intermediate said areas extendingupwardly a substantial distance above said flange, said reinforcementcomprising a fiat bar, the under face of said bar being flat on saidflange and providing said contacts, the width of said bar being greatestat said areas and being least at the highest point between said areas.

5. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a plurality ofspaced intervals and welded thereto at the areas of said contacts, theportions of said reinforcement intermediate said areas extendingupwardly a substantial distance above said flange, said reinforcementcomprising a flat bar, the under face of said bar being flat on saidflange and providing said contacts, the amount of metal of said bar atsaid areas being greater per unit length than intermediate said areas.

6. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a pluraliy ofspaced intervals and welded thereto at the areas of said contacts, theportions of said reinforcement intermediate said areas extendingupwardly a substantial distance above said flange, said reinforcementcomprising a flat bar, the under face of said bar being flat on saidflange and providing said contacts, said bar having a greater transversecross sectional area at said areas than intermediate said areas.

'7. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a plurality ofspaced intervals and welded thereto at the areas of said contacts, theportions of said reinforcement intermediate said areas extendingupwardly a substantial distance above said flange, said reinforcementcomprising a flat bar, the under face of said bar being flat on saidflange and providing said contacts, and relatively small shearconnectors welded to said flange adjacent to said welds.

8. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a plurality ofspaced intervals and welded thereto at the areas of said contacts, theportions of said reinforcement intermediate said areas extendingupwardly a substantial distance above said flange, said reinforcementcomprising a flat bar, the under face of said bar being fiat on saidflange and providing said contacts, and relatively small shearconnectors welded to said flange adjacent to said welds, said connectorshaving flat faces and relatively narrow edges and being welded inupstanding positions.

9. In a composite metal-concrete structure a metal beam having an upperflange, a continuous sinuous metal shear reinforcement welded on saidflange, said reinforcement contacting said flange at a plurality ofspaced intervals and welded thereto at the areas of said contacts, theportions of said reinforcement intermediate said areas extendingupwardly a substantial distance above said flange, said reinforcementcomprising a flat bar, the under face of said bar being flat on saidflange and providing said contacts, and relatively small shearconnectors welded to said flange adjacent to said welds, said connectorshaving flat faces and relatively narrow edges and being welded inupstanding positions under said reinforcement intermediate said areas. aCLEMENT P. CUENI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

